Metal cans for containing beer and beverage products as well as a wide variety of other consumables are in widespread use. Generally the cans are comprised of one open ended piece that forms the can body and a second piece which is utilized for sealing the can. Aluminum and steel are materials of choice for the fabrication of many of these cans. The outer surfaces of the cans are typically supplied with a label or other printing which is then overvarnished to protect the printing as well as the surface of the can. In addition, an interior coating is sometimes applied to the can in order to protect against product contamination.
After application of the printing and other coatings to the can surfaces it is necessary to properly cure the cans by baking. After baking, the cans are then cooled prior to being utilized. To effect proper curing of the various can coatings the cans are carried through a pin oven on a pin conveyor which is essentially an endless conveyor having a multiplicity of pins over which the can bodies are placed for travel through the curing oven and cooler.
In modern pin oven operations cans can typically move through the oven at speeds of up to 1500 cans per minute. One of the limiting factors as to the number of cans that can be moved through an oven is the speed with which the cans can be removed from the pins on which they are carried after the cans emerge from the cooler attached to the oven.
In the past, for further processing, the cans have been removed from the pin conveyor by an apparatus which is referred to in the art as a pin stripper or, more simply, a stripper. A common type of stripper employs a moving vacuum chain to which the bottoms of the can bodies may be drawn to effect removal of the cans from the pin conveyor. The vacuum chain is made of plastic and is run in a dry condition along wear strips. Such type of stripper has been successfully run with desirable vacuum chain performance at vacuum chain speeds up to about 650 feet per minute, i.e., at can removal speeds up to about 1500 cans per minute given a typical conveyor pin spacing of 5.25 inch. At higher speeds, excessive wear of the vacuum chain links and to a lesser extent the wear strips has been encountered, and the heat and dynamic forces involved may even cause the chain link plastic to flow or melt. An impetus to keeping wear at a minimum is not only the cost factor involved in replacing worn chain links and/or wear strips, but also the substantial down time required to replace worn links and/or wear strips. It would be most desirable to be able to increase stripper speed and can removal rate while at the same time maintaining the integrity of the pin stripper chain and wear strips in order not only to improve and increase can production capability, but also to reduce and minimize maintenance and down time.